Advanced air bag requirements have resulted in the implementation of passenger occupant classification sensors. Two current occupant classification sensor systems are structure based sensor systems and bladder systems.
Structure-based occupant classification sensor systems include sensors designed in the lower seat structure or seat base, whereas bladder systems are non-structure based and include bladders placed between seat foam and a seat pan. Structure-based systems measure the weight on the seat (including bottom and back cushions) for determining a classification for the front-seat passenger occupant, for example, child, adult, etc., and can also be used for determining a classification for the driver occupant, for example, small adult (5th%), medium adult (50th%), and large adult (95th%).
For these systems properly to measure occupant weight, the seat must not contact any adjacent systems (e.g. center console, door panel) and should be unconstrained. Occupant classification sensor system measured error results from adjacent system contact with the seat and is usually measured in pounds or kilograms. Most of the above specified adjacent system contacts produce only small amounts of occupant classification sensor measurement error.
Large errors may be generated, however, when a vehicle power seat is motored or driven into or onto an object that stops the seat movement prior to normal seat travel, and the seat motor continues to apply a force into the seat structure. Examples of items that may cause these measured errors include: a power seat lowered onto an object stuck under the seat and fore or aft seat movement into an object directly behind the seat (e.g. cargo behind the seat). These large measured weight errors can lead to improper occupant classification and improper pyrotechnic deployment strategies.
Similar difficulties also exist for manual seats where the operator adjusts the seat, which induces forces on the seat structure as a result of contacting objects. These forces generally result in system measurement error.
Therefore, it would be desirable to provide an improved occupant weight detection system to decrease the probability of improper safety device response.